The present invention is directed to biological methods, processes and apparatus for producing organic acids, alcohols, and salts from the waste gas streams of certain industrial processes and more particularly concerns a process utilizing continuous gaseous substrate fermentation under anaerobic conditions to accomplish this conversion.
The conventional procedure for- producing organic acids, alcohols, and salts is chemical synthesis of petroleum-derived feedstocks. The rapidly escalating cost of petroleum has generated considerable interest in producing these valuable commodities by fermentative processes that utilize renewable or waste materials as the feedstock.
There is also growing concern over the massive amounts of atmospheric pollutants and greenhouse gases produced by conventional industrial processes. The Environmental Protection Agency recently estimated that over six million metric tons of carbon monoxide and nearly four million metric tons of hydrogen were discharged annually by the industrial complex. A substantial portion of this waste carbon monoxide and hydrogen are the result of carbon black manufacture and coke production, roughly 2.6 million metric tons of CO and 0.5 million metric tons of H.sub.2. Large amounts of carbon monoxide or hydrogen are also produced by the ammonia industry (125,144 metric tons of CO in 1991), petroleum refining (8 metric tons per thousand barrels), steel mills (152 pounds per metric ton of steel produced), and sulfate pulping of wood (286 pounds per ton of pulp). In 1991, the adipic acid industry generated 40,773 metric tons of carbon monoxide that was burned for fuel value or flared. In many cases, these gases are discharged directly to the atmosphere, placing a heavy pollution burden on the environment.
Typically, the waste gases from the manufacture of industrial products are released at low pressures and temperatures. Current technology can not utilize these dilute gases under such conditions. Adapting existing technology to separate and recover hydrogen or carbon monoxide from these waste streams would be expensive and impractical.
In light of the foregoing, there is a need for a cost effective and practical method and apparatus for utilizing the above-described waste gases and for producing organic acids, alcohols and salts by other than chemical synthesis of petroleum derived feedstocks.